Q&A: The science behind personal genetics testing

IOWA CITY, Iowa (AP) — A growing number of universities are offering classes on personal genetics to educate students about a medical field that is becoming increasingly important as the price of genetic testing drops. Here's a look at the basics:

Q: What is genetic testing and genotyping?

A: A genetic test analyzes DNA to look for a specific gene to test for the presence of a condition, such as Huntington's disease. Genotyping goes far beyond that, analyzing several or even thousands of variants across an individual's full set of genes, known as the genome.

Q: How can you get such testing done?

A: Medical providers use the testing routinely. It helps them diagnose patients who have symptoms of a disease, screen newborn infants for disease risks, tell parents whether their unborn child will have a genetic condition, and determine the amount and type of medicine best suited for a patient.

But what is becoming more available and common is testing done by private companies marketing services directly to consumers, such as 23AndMe and AncestryDNA. These tests typically analyze thousands of different variants but do not look at the entire genome. The tests can cost $99 to more than $1,000, depending on the extent of testing done. 23AndMe and AncestryDNA require individuals to submit saliva samples, and initial results can be available within six weeks.

Q: What can the results show?

A: The results can show whether individuals are at increased risk for a range of diseases; whether they are a carrier for hundreds of genetic conditions; whether they are predisposed to have certain physical traits; where one's ancestors come from; how they may respond to certain drugs.

Q: What are some practical ways this can help?

A: The information can help diagnose potential health problems sooner. Individuals may be able to take steps to avoid behavior that may trigger health problems for which they know they're at risk. Couples who learn they are carriers for the same disease may conceive with egg or sperm donors to avoid passing it to children. Individuals may be able to identify and meet relatives they did not know.

Q: What are potential downsides?

A: Scientists caution that the tests can be misleading because many genetic discoveries have yet to be made, which means some results may falsely reassure or needlessly alarm people. But the tests can also deliver shocking information — individuals can learn they are likely to develop diseases that have no cure, have siblings they never knew about, or that the man who raised them is not their father. There are also numerous ethical and privacy considerations. One's relatives do not need to give consent for the tests, even though they may learn distressing information. Companies ask for consent to use their customers' DNA in research, and there's always the risk of a privacy breach.